Aripiprazole, 7-{4-[4-(2,3-dichlorophenyl)-1-piperazinyl]-butoxy}-3,4-dihydro carbostyril or 7-{4-[4-(2,3-dichlorophenyl)-1-piperazinyl]-butoxy}-3,4-dihydro-2(1H)-quinolinone, is an atypical antipsychotic agent useful for the treatment of schizophrenia (U.S. Pat. No. 4,734,416 and U.S. Pat. No. 5,006,528). Schizophrenia is a common type of psychosis characterized by delusions, hallucinations and extensive withdrawal from others. Onset of schizophrenia typically occurs between the age of 16 and 25 and affects 1 in 100 individuals worldwide. It is more prevalent than Alzheimer's disease, multiple sclerosis, insulin-dependent diabetes and muscular dystrophy. Early diagnosis and treatment can lead to significantly improved recovery and outcome. Moreover, early therapeutic intervention can avert costly hospitalization.
According to Example 1 of Japanese Unexamined Patent Publication No. 191256/1990, anhydrous aripiprazole crystals are manufactured for example by reacting 7-(4-bromobutoxy)-3,4-dihydrocarbostyril with 1-(2,3-dichlorophenylpiperadine and recrystallizing the resulting raw anhydrous aripiprazole with ethanol. Also, according to the Proceedings of the 4th Japanese-Korean Symposium on Separation Technology (Oct. 6-8, 1996), anhydrous aripiprazole crystals are manufactured by heating aripiprazole hydrate at 80° C. However, the anhydrous aripiprazole crystals obtained by the aforementioned methods have the disadvantage of being significantly hygroscopic.
The hygroscopicity of these crystals makes them difficult to handle since costly and burdensome measures must be taken in order ensure they are not exposed to moisture during process and formulation. Exposed to moisture, the anhydrous form can take on water and convert to a hydrous form. This presents several disadvantages. First, the hydrous forms of aripiprazole have the disadvantage of being less bioavailable and less dissoluble than the anhydrous forms of aripiprazole. Second, the variation in the amount of hydrous versus anhydrous aripiprazole drug substance from batch to batch could fail to meet specifications set by drug regulatory agencies. Third, the milling may cause the drug substance, Conventional Anhydrous Aripiprazole, to adhere to manufacturing equipment which may further result in processing delay, increased operator involvement, increased cost, increased maintenance and lower production yield. Fourth, in addition to problems caused by introduction of moisture during the processing of these hygroscopic crystals, the potential for absorbance of moisture during storage and handling would adversely affect the dissolubility of aripiprazole drug substance. Thus shelf-life of the product could be significantly decreased and/or packaging costs could be significantly increased. It would be highly desirable to discover a form of aripiprazole that possessed low hygroscopicity thereby facilitating pharmaceutical processing and formulation operations required for producing dosage units of an aripiprazole medicinal product having improved shelf-life, suitable dissolubility and suitable bioavailability.
Also, Proceedings of the 4th Japanese-Korean Symposium on Separation Technology (Oct. 6-8, 1996) state that, anhydrous aripiprazole crystals exist as type-I crystals and type-II crystals; the type-I crystals of anhydrous aripiprazole can be prepared by recrystallizing from an ethanol solution of aripiprazole, or by heating aripiprazole hydrate at 80° C.; and the type-II crystals of anhydrous aripiprazole can be prepared by heating the type-I crystals of anhydrous aripiprazole at 130 to 140° C. for 15 hours.
By the aforementioned methods, anhydrous aripiprazole type-II crystals having high purity can not be easily prepared in an industrial scale with good repeatability.